A. Field of the Invention
The present invention relates to a method and apparatus for performing optical serial-to-parallel conversion. In particular, the present invention uses second harmonic generation to perform high-speed optical time domain demultiplexing and optical code recognition.
B. Description of Related Art
During the past decade, fiber optic communication technology has been developed and commercialized at virtually unprecedented rates. Current long-haul systems operate at data rates up to 1.7 GB/s. Plans call for the introduction of 2.4 GB/s long-haul systems in the near future and rates of up to 10 GB/s are being demonstrated. For systems with shorter fiber spans, such as local-area and metropolitan-area networks, there is no fundamental reason why fibers cannot support data rates which exceed these rates by at least two orders of magnitude. In fact, it can be shown that, for transmission links on the order of kilometers, commercially available fibers can support data rates exceeding 100 GB/s on a single optical carrier in the 1.3 micrometer wavelength range without resorting to operation at exactly the zero-dispersion wavelength. However, at these data rates, electronic components are unable to generate, interpret or switch the data.
In view of the speed limitations of electronics, it is evident that, to implement high speed communication systems, it is necessary to have a high-speed optical signal processing technology to compliment the high-speed optical-transmission technology. In addition, new system concepts which are compatible with the higher data rates and with the optical hardware must be developed.
One concept of interest to researchers attempting to develop hardware to mate electrical and optical signal processing is second harmonic generation (SHG) and waveguide SHG in particular. Investigators Normandin and Stegeman have authored a number of papers detailing the occurrence of waveguide SHG. See for examples, R. Normandin and G. I. Stegeman, Non-Degenerate Four-Wave Mixing in Integrated Optics, Optics Letters, Vol. 4, No. 2, February 1979; Picosecond Signal Physics Letters, 36(4) Feb. 15, 1980; and P. J. Vella, R. Normandin, and G. I. Stegeman, Enhanced Second-Harmonic Generation by Counter-Propagating Guided Optical Waves, Applied Physics Letters 38(10) May 15, 1981. Normandin and Stegeman demonstrated waveguide SHG in strongly non-linear optical materials by inserting an optical pulse at one end of the waveguide and another optical pulse at the other end of the waveguide. When the two injected signals collided, they produced a second harmonic wave which propagated perpendicular to the waveguide surface.